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The interaction of urea with the generic class of poly(2-hydroxyethyl methacrylate) hydrogels

โœ Scribed by Pinchuk, L. ;Eckstein, E. C. ;Van De Mark, M. R.

Publisher
John Wiley and Sons
Year
1984
Tongue
English
Weight
887 KB
Volume
18
Category
Article
ISSN
0021-9304

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โœฆ Synopsis

Abstract

Work reported here shows that, contrary to reports in the literature, hydrogels made from pure poly(2โ€hydroxyethyl methacrylate), pHEMA, at crosslinker content greater than 0.15 mol % do not swell above the usual equilibrium values of 39โ€“42% water content in aqueous urea solution. However, hydrogels containing small (impurity) amounts of methacrylic acid (MAA) do swell dramatically (approximately 90%) in dilute urea solution, but not directly due to the urea. The urea decomposes to produce ammonium ions, thus raising the pH of the solution. Ionization of MAA occurs above pH 6, causing electrostatic interactions within the gel. The grossly swollen state of these gels represents an internal equilibrium among forces due to rubber elasticity, polymerโ€”polymer/solvent affinity, and electrostatic interactions.

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